What determines the set point of a PSV

[jboy]

Can anybody tell me if there are certain rules of thumb used when determining the set point of a PSV. The reason i ask this is because i have recently come across the following situation.
A heating medium system has a expansion drum operating pressure of 2.4 Bar. Yet the Psv are set at 8 Bar. How is this pressure determined and why is it almost 4 times the operating pressure.
Thankyou
JBoy

 

The set point of a safety relief is typically determined by the MAWP (maximum allowable working pressure) of the vessel. This should be recorded on the nameplate of the vessel. The set point of the relief device should be set at or below this point.

 

[rusman]

Agreed with Samed. It shall be set at the Design Pressure of the protected equipment, or lower than the design pressure. The design pressure is determined by the operating pressure of the system with additinal factor, normally 10 % higher than max operating press.

Hope this help

thanks

rusman
man@rwsb.po.my
process consultant

 

[JAlton]

While the typical setting of a PRV is at MAWP, the Code allows for it to be set "at or below MAWP". The PRV in question could be set lower. Then the question becomes, how much differential do you need between the operation pressure of 2.4 bar and the opening pressure of the PRV?
Typically it is 10%. This allows for small transients without lifting the PRV.

J. Alton Cox
President
DeLuca Test Equipment

http://www.delucatest.com